PHILADELPHIA, April 21 -- Sens. Hillary Rodham Clinton and Barack Obama offered Pennsylvania voters their closing arguments on Monday, winding down a nearly two-month campaign in the state that has done little to bring clarity to the Democratic presidential contest.

In stops statewide, Clinton continued to say that she is best prepared to serve as president, while Obama and his aides sought to play down expectations for a race in which victory appeared to be slipping out of his reach.

"I'm predicting it's going to be close and that we are going to do a lot better than people expect," Obama said, as his campaign tried to shift the focus to upcoming contests in North Carolina and Indiana, and to his lead in the overall delegate count.

While Obama planned to head straight to Indiana after the Pennsylvania primary election on Tuesday, Clinton scheduled a nighttime victory rally here. She made a pair of national television appearances -- with MSNBC's Keith Olbermann and CNN's Larry King -- and used the opportunity to tell undecided superdelegates that she would be the more electable candidate in the fall.

Seeking to close the deal in a campaign that has become increasingly vitriolic in the past few days, Clinton also began a final ad, titled "Kitchen," designed to remind voters that only she is ready to handle the job of commander in chief. The spot showed an array of images designed to demonstrate moments of great peril for the nation, including headlines from the attack on Pearl Harbor and images of Osama bin Laden and Hurricane Katrina. It never mentions her rival by name, but the subtext is clear: Obama, who appeared off-balance when he came under tough questioning in a debate last Wednesday, is not up to the rigors of the role. "Harry Truman said it best: If you can't stand the heat, get out of the kitchen," the ad says.

During an appearance in McKeesport on Monday evening, Obama pushed back, pointing to Clinton's vote to authorize the war in Iraq.

"There are three candidates left. Who do you want answering that 3 a.m. phone call: The person who got Iraq wrong or the person who got Iraq right? . . . We need someone who knows how to use diplomacy," he said. "We will make America more safe, that's my commitment when I'm president of the United States of America."

In an earlier town hall-style meeting at a community college in suburban Philadelphia, Obama barely mentioned Clinton, suggesting only that her campaign is based on the status quo while his is a true grass-roots movement that would "get out of the typical pattern of the last 20 years."

"Not all of us have talked about the need to change the way Washington works," he said. "One of the key distinctions in our campaign is that it has been built from the ground up."

Moving from a diner in Scranton to a wealthy Philadelphia suburb to a commuter college southeast of Pittsburgh, Obama toned down the campaign atmospherics -- only a late-night appearance at the University of Pittsburgh was designed to draw thousands of attendees. His advisers pointed to polls showing Clinton with an apparently comfortable lead over the weekend.

"I'm not here saying I expect us to win tomorrow; I don't think anybody expects us to win," David Axelrod, Obama's chief strategist, said aboard the campaign jet en route from Philadelphia to Pittsburgh. "But I think we can make a good showing and do well with delegates."

The silver lining for Obama is that, while Clinton remains the heavy favorite to win the popular vote, her net pledged delegate gains in Pennsylvania are not likely to be significant, and possibly no higher than 10, according to campaign and outside estimates.

The state has a two-part primary ballot, with voters choosing a presidential candidate and also picking from a slate of local delegates. Essentially, each of the state's 19 congressional districts runs a separate contest for delegates, weighted according to turnout in recent elections. A total of 103 delegates will be awarded according to each district's popular vote, while the remaining 84 will be distributed according to the statewide popular vote, or as unpledged superdelegates. In Democratic strongholds, such as the 1st and 2nd districts, both in Philadelphia, participation rates are high, and those districts allocate seven and nine delegates, respectively.

Obama could win seven of the nine delegate at stake in the 2nd District, and four of seven in the 1st, his campaign estimates.

By contrast, the 12th District, in central Pennsylvania, where Clinton is expected to perform well, allocates five delegates; the 9th District, also pro-Clinton, awards three. Five other districts award four delegates each, while one (the 6th) awards six. Under party allocation rules, unless Obama loses by large margins in these even-numbered districts, he could split the delegate take.

Regardless of the delegate landscape, Clinton campaign advisers, exuding confidence on the eve of the Pennsylvania primary, said an Obama defeat here on Tuesday will raise new doubts about his ability to win the general election.

Clinton had seemed to settle the question of Obama's electability during last week's debate. Facing mounting anxiety among Democrats that she would rather destroy the eventual nominee than withdraw from the race, Clinton answered "Yes, yes, yes" when asked whether Obama could defeat Sen. John McCain, the presumptive Republican nominee, in November if he won the nomination.

On Monday, however, Clinton aides held a conference call to discuss the stakes of the Pennsylvania race. Their hope -- their only hope, some have said -- is to use a big victory in the state to persuade superdelegates to turn their way for fear of losing the general election.

"He is doing everything that he can to win -- not to finish closely, not to do well, to win," said Howard Wolfson, a senior aide. "He is trying to knock Senator Clinton out of this race. He has outspent us 3 to 1. . . . He has gone sharply negative. There are so many negative ads he has up that I can't even keep track of them. . . . If he does not win after having outspent us so dramatically, it would raise very serious questions about whether Senator Obama can win the big swing states that any Democrat would have to win in November."

Appearing with his wife at a rally in Pittsburgh, former president Bill Clinton dismissed complaints that the prolonged primary battle is hurting the party's chances in November.

"If we were under the Republican system, which is more like the Electoral College, she'd have a 300-delegate lead here. I mean, Senator McCain is already the nominee because they chose a system to produce that result, and we don't have a nominee here, because the Democrats chose a system that prevents that result," he said. "Disenfranchisement is not a good strategy for Democrats," the former president said. "We do a better job when people are in power. So I just don't agree with that."

Kane, with Obama, reported from Blue Bell and McKeesport. Staff writer Shailagh Murray, with Obama in Scranton, contributed to this report.